Why..? Plus, it'd make suiting up a lot more difficult.............again

The same type of suit from TDK couldn't be adapted to fit a stronger, athletic figure? Navy Seals are around Bale's size in BB and they wear a similar type of kevlar at times. It would work. The only reason I could think of for the decrease in weight is Nolan's attempt at explaining what that type of night life is doing to him physically.